Filtering apparatus



Dec. 18, 1956 R. CUMMINGS FILTERING APPARATUS R. Y. 1 m m t N9 R e E .n O m m n m A m m e a m 9 c a 6 m 2 Filed Jan. 5. 1945 Dec. 18, 1956 R. CUMMINGS FILTERING APPARATUS Filed Jan. 5, 1945 INVENTOR. A 055 CZ/m/77/f7g5 ATTORNEY.

DeC. 18, 1956 R. CUMMINGS FILTERING APPARATUS Y INVENTOR. F055 Camm/flgfi 5 7 /0 4/ wwg w 4% Filed Jan. 5, 1945 ATTORNEY;

' D 1956 R. CUMMINGS FILTERING APPARATUS 6 Sheets-Sheet 4 Filed Jan. 5. 1945 INV EN TOR. 07/77/2795 ATTORNEY.

Dec. 18, 1956 R. CUMMINGS 2,774,479

FILTERING APPARATUS Filed Jan. 5, 1945 6 Sheets-Sheet 5 Maw Dec. 18, 1956 Filed Jan. 5, 1945 R. CUMMINGS 2,774,479

FILTERING APPARATUS 6 Sheets-Sheet 6 filtefillg devices unsatisfactory for United States Patent FILTERING APPARATUS Ross Cummings, Berkeley, Calif assignor to the United States of America .as represented by the United States Atomic Energy Commission -APPliCElfiOIlJ3Hll3W 5, 1945,3Serial No. 571;421 1 4 Claims. (Cl. 210-184) This invention relates to filtering systems, and *partic- 'ularly to filtering apparatus employing -s0-"call'ed *thitn'ble or candle filters in a manner designed to handle extremely valuable precipitates substantially Without-any loss.

'In separating such precipitates from a liquid suspending medium, the volume of slurry -to be-'=handled"-ma-y be relatively small as compared with that-handled in most commercial filtration processes, and yet sul'licient ly great -to'-require more efficient filtration' methods and apparatus than are commonly available in'allaboratory. The losses bf 'pmcipitate encountered in using most commercial fil- -teringdevices, as a result of incomplete precipitate separation and because of difficulties errcounteredin-comp'letely removing the precipitate from the filtering'mediurn, '-in-cleaning the tanks, etc. and as a 'resu'ltof splashing, 'drippin'g, and other accidental losses, contribute to make such apparatus unsatisfactory for =use on 'a small scale-in the recovery of valuable material requiring the maintenance or precipitate losses at substantiallyzero.

*It is an object 'ofthis invention to -providea coinbination filtering, washing, and-drying system capable'mf elli- 2,774,479 Patented Dec. 18, 1956 Fig. 3 is an end elevation of the structure shown in Fig. 2;

Fig. t isan enlarged vertical section taken on the line -4 4 of Fig. 2 and-showingiin-detail .the filter supporting structure and an' associated valve mechanism;

Fig. 5 "is a'perspective view, partly in sect-ion,showing on an enlarged scale the valve mechanism of 'Fig. 4;

Fig. 6 is an end elevation of the filter supporting structure and filter moving apparatus shown in Fig. 1, partly in section taken along the line 6-6 of Fig. 1;

Fig. 7 "is a view similar to '-Fig.' 6, but taken along the 'line 7'-7 of Fig. 1, showing the filter supporting and filter movingapparatusina'diflferentposition;

Fig. -8 is a side elevation of the apparatus shown in Fig. i6, withcertain-parts broken away for clarity;

Fig; -9-is a schematic plan view-of the tanks -of Fi s. 1, 2, and 3 showing the various sequential positions of the th'irr'il'ile filters during the steps of filtering, washing, and drying-andshowing the sequence in which suction is app'lied'toisuction =Iines connected "to the thimble filters;

: Fig. lO is a view-similarto Fig. '9 but shows how the tank-and the use of suction lines may be modified for =einploying' the apparatus according to :a dilferent system of operation; Y Eig. fl' l is aview similar to -Fig. 9 "but showshow the tank, the suction tubes, "and the use of thesuction tubes may be modified *for employing the apparatus according ftostill*anothersystem'of operation; and V V Fig. 1'2 shows a schematicpartial plant diagram for the embodiment "of the invention represented by *Fig, 11, including suction and positive pressure systems adapted ."forcoQperatiVe association with a pai'r of filter elements.

-eiently handling a slurry which is ava'nssle either in A *batches or in "a small but constant llowof'mati'ial.

--It'-i-s a further-object of thisinven'ti'on to accomplish tlre foregoing with a maximum efiiciency of ise'paration and with a minimum hold-up of-materialduring-"the filtering,

washing-and drying steps.

A further object'of the inventionisdoprovideapparatus capable of accomplishing a maximum throughfpt'it of material under conditions o'f'a igh separatingefliciency and minimurn hold up-of material. j

"-A fur'ther object is 'to provide apparatus-capable of carrying out the filtering, washing, and arring '-'s't'ep's in "such 'a' manner that substantially none of 'ihe preipitate -"to be filtered will be" lost as a *restilt "dfsplashing-drip- -ping, absorption, adherence -todiscafded' worn out, filtering media, or other such'causes'whiclrmakeconventional the handling ofwaluable materials.

"Afur'ther objectis'toprovide apparatus which, though in large partx manually controlled, is'eqtiippe' tl vviih eertain protective features adapted to minimize-the chances ii that -"the-'pro'cess'-will be disrupted or that warmers-mateeralembddiments thereof are disclosed inshersnowin g *deta'ileddescription and in -'the*drawings in which:

Figure 'l is an elevation, partly insectionfshowin'g a series of tanks "or tankcompartments and one-fdf apair of "associated filter-elements, its supporting str'ueture, "and apparatus for moving the same from an; to tank;

"Fig. 2 is a 'plan' viewpartly in"set:tio'n takenalongthe V Referringparticularly to Figs. 1, 2, and 3, a receptacle, generally designated '1, made of'any suitable non-porous "material'chemically resistant to the solutions to be con- 'tain ed'therein, is divided by three partitions 2, 3, and -'4 "in'to four tanks or compartments 5; 6, 7, and '8. The tanks '5, '6, and 7 are "respectively adapted to contain a slurry to j be filtered, asuitable wa'shsolution, and a suitable drying liquid' such as a -volatile1, anhydrous, organic solvent; and the tank '8 --is adaptedto containa ipair of scraper units, generally-designated Z9 and :described inn-lore detail'here'inafter. "The bottoms of the "first'th'reeftanks "5, 6, and 7 are sloped toward outlet ope ning's 11; to which are connected outlet pipes 12 pro- 'vicled with'suitable valves 13. Each of these three tanks S, 6, and 7 fistalso'provided with anopening 14 communicating *w'ithapipe 15 for supplying to thatitank the slurry,

*atrtsopp'osite end and driven bya motor.24. Brackets *25, rigidly mounted' in :any suitable, manner upon the recep'ta'clje' 1, "support the bearings 18, '19, and 23; I

fAsmn'tionedabme, thefourth tank' 8 is provided with :apparatus'for' removing'the filter cake from each 7 of two thirriblefiltbrs to be employed in association with the 'first three tanks 5,6, and "7.- This apparatus 29 com- "prisesa supporting framework 30 adapted to support "two sets dfscraper blades, each set comprising 'four blades 31. Each' of :the blades -31 is mounted on the supporting 'frameWOi'k by slotted' -arrns 3-2 suitablysecured to the Fblades, "as bywelding, and to the supporting framework 30 E by extensions passing through the-supporting framewdi'k and-riveted 1 on the opposites'ide"thereof, as shown jacent the bottom of the latter. also includes a non-rotatable assembly that supports the at 33. Below each set of scraper blades, the tank 8 is provided with outlets 9 through which material removed by the blades 31 may fall into any suitable container (not The receptacle 1 and its associated apparatus described above is assoeiated with two identical thimble filter elements 36 and 37, preferably made or aporous material such as electrically fused alumina. These filter elements, supported side by side as shown in Fig. 3, are adapted to be dippedtogether into the slurry tank and to have suction applied to the insides of the filter elements to draw filtrate through their porous walls and to cause a filter cake to be loaded upon the outsides thereof. The filter elements carrying a cake of precipitate are adapted to be lifted vertically out of the slurry tank 5, moved horizontally into vertical alignment with the adjacent wash tank 6, and lowered vertically into the wash solution c ntained therein. In this position suction is again applied tothe insidesof the filter elements to cause wash solution to percolate through the filter cakes to theinterior of the filter elements, displacing residual filtrate held by the filter cakes. The filter elements are then raised vertically out of the wash tank 6, moved horizontally-to positions in alignment with the next adjacent tank 7, and lowered into the drying liquid contained inthis tank 7. Suction is again applied to the insides of the filter elements to cause the drying liquid to percolate through the filter cakes to the interior of the filter elements, displacing residual wash solution held by the filter cakes. The filter elements are then raised vertically out of the drying liquid tank 7, this time with suction still applied, whereby air is drawn through the filter cakes causing the drying liquid to evaporate and leaving the filter cakes in a dry condition. The filter elements are then moved horizontally to positions in vertical alignment with the two sets of scraper blades 31 in the scraper tank 8 and are lowered into contact with the scraper blades. By rotating the filter elements through about a quarter of a turn. while they are'in contact with the scraper blades, the filter cakes are removed from the filter elements and fall through the outlet openings 9 below the scrapers, where the dry precipitate may be collected in any suitable manner.

The two filter elements 36 and 37 are independently supported side by side above the receptacle 1 by two filtering columns, generally designated 34 and 35, which .are mounted for independent movement along parallel paths above the tanks and into alignment therewith in sequence. Referring for the moment only to the filtering column 35 shown in detail in Figs. 1 and 4,itjwill be ob- ,servedthat the filtering column includes a rotatable assembly consisting of the following principal elements: A lowermost thimble filter element 37; a filter head 38 to which the filter element is secured; a lower metal tube 39 integral with and supportingithe filter head 38; an intermediate supporting metal tube 40 to which the lower supporting tube 39 is detacbably connected; a rotatable portion of a valve unit, generally designated 60, detachably. supporting the tube 40; a filtrate tube communicating with a port 57 of the valve unit 60 and comprising a transparent glass section 50 extending through the intermediatesupporting tube 40 and a metal section 45 coupled to the lower end of the glass section 50 and extending through the lower supporting tube 39, through the filter head 38, and through the filter element 37 to a point ad- Each filtering column rotatable assembly and that consists of a non-rotatable portion of the valve unit 60 (partially enclosed by the heavy black line AB in; Fig. 5) and a non-rotatable upper supporting tube 80 rigidly mounted in the nonrotatable portion of the valve unit. A separate carriage mechanism, generally designated 100, is provided for each filtering column. Each carriage. 100 supports-its associated filtering column for vertical sliding movement between an upper and a lower position (both show; in,

Fig. 1) so that the filtering column may be lowered intoand raised out of a tank in alignment with and immediately below it, and is adapted to move along a horizontally extending track 101, when its associated filtering 5 column is in its raised position, to move the filtering col umn horizontally and align it with an adjacent tank into which it may then be lowered. Separate, identical, parallel tracks 101 are provided for the two carriages 100, and each track is rigidly supported in proper alignment with the receptacle 1, as by vertical columns 102 and 103. Since the two assemblies of filtering columns and their associated carriages and tracks are identical in construction, only the assembly with which the above described filtering column 35 is associated has been shown completely in the drawings. The location of the assembly with which filtering column 34 is associated is apparent from Figs. 2 and 3, showing portions of both assemblies in side by side relation.

As shown in Fig. 4, the filter element37 may be mounted on a stainless steel filter head 38 by means of a suitable cement 43. The filter head may be secured by welding to the lower supporting tube 39, also preferably made of stainless steel, or the filter head and lower supporting tube. maybe made integral as shown in Fig. 4; but the lower supporting tube is fastened to the intermediate supporting tube 40 by screw threads 41. The lower supporting tube carries a suction tube coupling assembly comprising a generally disk-shaped stainless steel member 42 welded to the upper end of the lower supporting tube 39. The coupling member 42 is provided at its center with ahollow boss 44 in which is mounted a stainless steel suction tube 45 communicating with a passageway 46 through the boss 44. The suction tube 45 passes through an aperture 47 in the filter head 38 to the inside of the filter element'37, terminating near thebottom thereof. The passageway 46 in the boss 44 also extends through a resilient ring 48, made of rubber or other suit- .able cushioning material, that provides a seat for a connecting suction tube 50, that extends into the hollow boss 44 and tightly engages the resilient ring 48 when the lower supporting tube 39 is screwed into the intermediate sup- .portingtube 40. With this arrangement, the filter elernent 37, the filter head 38, the lower supporting tube 39, .and the associated suction tube may be detached from 45 the intermediate supporting tube 40 in order to replace .the filter element without disassembling the entire lower portion of the filtering column.

7 The intermediate supporting tube 40 is provided with a pair of window openings 51, and the suction tube 50 is 50 'made of glass or other transparent materiahso that when the filter element 37 is lowered into one of the compartments 5, 6, or 7, as shown in Fig. 1, and suction is applied .to the suction tube 50, the passage of liquid through the tube 50 may be observed and the entrainment of any solid material visually detected. 7

g The intermediate supporting tube 40 threadedly engages at its upper end a generally cylindrical block 52, which in turn threadedly engages the interior of a cylindrical valve housing 53 and is held therein against unscrewing by a set screw 54. An annular groove 55 around the upper end of the block 52 accommodates a rubber packing ring 56, which bears against the inner surface of the cylindrical valve housing 53 to provide an air seal. The glass suction tube 50 is secured to the cylindrical block 52 r in communication with the valve port 57 centrally located in the cylindrical block. The port opening is enlarged to accommodate a neoprene ring 61, a softrubber ring 62 that fits tightly around one end of the glass tube 50, 7 and apacking gland 63 that surrounds the glass tube 50 and is adapted to be screwed into the port 57 to force the soft rubber ring 62 into sealing contact with the neoprene ring 61 and with the glass tube 50. The top of the valve housing 53 is provided with a centrally disposed circular opening 64, and an upper, non-rotatable, supporting tube cameras for the valve :unit and associated ifilterrassembly is mounted in the :opening 64 in :a manner to be dese'rib'ed.

:As 'stated above, the valve un'it 60 :comprises a' rotata'ble portion and -a non-rotatable portion, separated in Fig. 5 by a :heavy black line to facilitate visua'lizing the operation of =the assembly. The non-rotatable portion of the as sembly comprises a stainless steel collar 65 provided adjacent its upper, inner periphery with a seat 66 in which the lower end of thetubularsupport 80 is rigidly secured, :as by welding. The lower end of the collar 65 is provided with a flange 67 thatdelines a seat for an asbestos packing ring 69 and is threaded on its=inner surface *to accom- =modate a correspondingly threaded, stainless steel, valve disk 68. When .the valve disk 68 is screwed into place in -the-collar-65,'the packing ring 69 is compressed against its seat in the collar to produce an airtight seal. An-annu- -lar rubber gasket 70 surrounds the tubular support 80 and rests on the top of the collar 65, and a flanged carbon bearing ring 71 Tests on the annular gasket 70 with the :flange of the bearing ring surrounding the gasket. The bearing ring 71 carries the weightof the rotatable p'ortion of the valve assembly and of the portion of the filtering column depending-therefrom. Friction between the bearing ring 71and the gasket ring 70 and between the gasket ring 70 and the non-rotatable collar 65 pre- '-vents'rotation of 'both the gasket ring 70 and the bearing ring 71. The valve disk '68 is pierced by three holes 72 parallel to the axis of the disk and uniformly spaced 'apart'along an are having its center at the center of'the disk. The lower end of each of 'three stainless steel suction tubes 81, '82, and 83 .is soldered, or otherwise rigidly secured, inone of the holes 72. The center of the lower surface of the valve disk 68 is relieved to provide a dome-shaped recess 73 in order to reduce the area of the surface of the disk 68 in'sliding contact with an adjacent element of the rotatable portion of the valve assembly. 7

The rotatable portion of the valve assembly includes the housing 53, the centrally apertured cylindrical block 52 rigidly mounted therein, a centrally apertured cushion disk 74 of rubber or the like, and a centrally apertured graphite flow-directing disk 75. The upper end of the cylindr'ical block "52 is cupped to receive the cushion disk 74 and the flow-directing disk 75 and these three parts are held against -.relative rotation by-two pins 76 '(Fig. 4). A stainless steel tube 77, secured by solder in a seat 78 in the central aperture of the flow-directing disk 75, .fits tightly in the neoprene ring 61 'with-theassistance of pressure exerted by the packing gland 63 vand constitutes -a liner for the port 57 toprotect the cushion disk 74 from contact with liquid flowing through the port. The tube 77 terminates just short of theehd of the glass tube 56) so as to avoid metal to glass contact between them. The upper end of the glass tube '50 abuts the neoprene ring 61 adjacent its inner periphery, and the lower end of this tube abuts the rubber ring 48. Pressure contact between the glass tube 50 an'd'the two rings 43 and 61 is brought about when the lower'supporting tube 39 is screwed into the intermediate supporting tube 49. c i

The valve unit'6i) is shown in 'Figs. 4 and 5 inadjusted condition to place the suction tube '50 in communication with the upper suction tube 81 through the port 57, through a passageway 79 in the flow-directing disk 75, and through the hole 72 in which the upper suction tube 81 is mounted in the valve disk 68. By rotating the rotatable portion of the valve unit 60,"in a clockwise direction as viewed from above -thevalve, through an angle equal to half the angular spacing of the holes '72 in the valve disk 68, the upper suctiontube 81 is disconnected and the passageway 79 is blocked oif by a solid portion of the valve disk. By continuing the rotation in the same direction through another angle equal to half the angular spacing of theholes 72in the valve "disk '68, the suction tube '82 is put in communicaition iwith the suction tube :50. A third :rotation of the rotatable :po'rtion of I'th'e valve unit 560, in the same dire'ction :and in Ethe same amount, disconnects the suction tube '82, and :a fourth "such rotation :puts the suction tube 83 in zicommunica'tio'h with the suction t-tibe 50. :Further rotation :of the rotatable portion :or the valve :unit 'in ithe same direction disconnects the suction :tube 583, (and, :during continued rotation through :an -=arc iof roughly 270, %the suction tube '50 is continuously blocked oif by the valve :disk 68. This "feature is desirable for reasons .to :be explained hereinafter.

:Suit-able cooperating markers "26 are placed on the top of ithe ivalve ihous'ing 53 and ion the upper supporting tribe :801t'o indicate the :positions -in which the tubes '81, -82, and '83 "are in communication with the tube 50.

:When ".the filtering columns are 'in their 'ra'ised 'p'osilions and are :being transferred from the third tank 7 etolpositi'ons .above the scraper tank 8, the suction *tube 5:33 is :in communieation'with the suctiontube-'50 so' that lair being sucked through the filter cake; to evaporate the drying material contained therein. The filter cakes :may become "sufiicie'ntly dry before the filtering columns are lowered to insert their associated filter elements into th'e'scraper ta'nk 8'sothat air draft-s are aptto blow' some .of the materi'al 'away. To guard against such accidental losses, a pair of generally-cylindrical glass shields 84 are mounted at thei'r'upper "edges in collars 85 respectively surrounding the two filtering columns sufiicientl'y Joosely sb that free sliding-contact between the collars andthefiltering columns is assured. Each collar 85includesa supporting-plate '86 that is flanged at two opposite ends to forrn gu'ides87 (Fig. ,3). YA trackst'ru'cture supports the collars 85 on the two adjacent filtering columns for sliding movement longitudinally of the receptacle 1 and 'parallel to "the direction of horizontal movement of the two columns. This track structure comprises two outer'tracks 8.8 and an inner double track 89' suitably supported above the receptacle 1 bytwojouter vertical columns 90 and .by.an inner vertical column/91 at each end of the tank. The columns 90 and 91 .are respectively provided at their lower ends with flanged 'plates 92 and $93, which are fastened to the end walls of the receptacle 1 by suitable fasteningzelements 94. Th8Sl1lldS.'84 may conveniently be mounted in-the mt lars 851With a suitable ceramic'cemen t 95. When-one of the filtering columns is raised,'-as shown in :do'tted 'lines'i'n'Fig. 1, .theassociated thimble .filter is drawn-up inside the glass shield 84. When the .filtering column "is moved horizontally from its raised position above-one tank to a position above an adjacent tank, the .shield supporting collar'85 slides horizontally along and'is supported by the tracks 88 and 89 and carries the shield "84 along with the thimblefilter to protect the filter cake carried thereby from disturbing air'drafts.

Each of the three suction tubes 81, 82, and 83in'the upper supporting tube 80 terminates a short distance above the valve unit 60 in a nipple 96. Rubber hoses 97, 98, and 99, attached to the nipples 96, constitute extensions of these three tubes 81,-82, and 83, respectively, and run through the remaining length of the upper supporting tube .80 and out the upper end thereof. Above the filtering column, the rubber hoses'97, 93, and 993m supported in any desired manner (not shown) -with,:sufiicient slack to permit their lower ends to move horizontallyand vertically'with the filtering column. g

Each of the rubber hoses 97, 98, and 99 leads to a separate source of suction (not shown), which-mayconsist of any conventional type of apparatus adapted to apply suction-toa container to draw liquid therethrough and to discharge the liquid into a collection tank. Thus, when the filter element 37 is lowered into the slurry tankS, and one of the suctionlines comprising a-rubber hose197 and ametal tube 81 is put into communication with the filter element through the suctiontubes SQ-and 45 in the intermediate and lower supporting tubes, filtrade from the slurry contained in this tank is drawn therefrom to a collection tank. Similarly, when the filter element 37 is lowered into the wash tank 6 and'the suction line to be associated therewith, comprising a rubber hose 98 and a metal tube 82, is put in communication with the filter element, wash solution is drawn from the .wash tank 6 to a collection tank. Similarly, when the filter element 37 is lowered into the drying liquid tank 7, and the suction line to be. associated therewith and comprising a rubber hose 99 and a metal tube 83 is put in communication with the filter element, the drying liquid is drawn from drying liquid tank 7 to a collection tank.

. Referring now to Figs. 6, 7, and 8, the carriage 100, supporting each filtering column to one side thereof, includes a framework comprising a pair of horizontally extending, parallel, upper bars 110 and 111 of rectangular cross section; a pair of horizontally extending, parallel, lower, bars 112 and 113 of rectangular cross section; a

pairof vertically extending parallel struts 114 and 115 holding the bars 110 and 112 in vertically spaced apart parallel relation and secured thereto by upper and lower pairs of bolts 122; a pair of vertically extending parallel struts 116 and 117 holding the bars 111 and 113 in vertically spaced apart parallel relation and secured thereto by upper and lower pairs of bolts 123; and, at each end of theframework, a pair of short, horizontally extending,

'upper and lower cross braces 118 and 119, respectively secured to the ends of the upper bars 110 and 111 and to theends of the lower bars 112 and 113 by cap screws 124. The lower, horizontally extending bar 112 adjacent the filtering column, at a point 120 approximately one-third of its'length from itsleft-hand end as viewed in Fig. 8, is notched to avoid interference with the movement of a pivoted locking arm 136, described hereinafter. A pair of upper, double-flanged wheels 125 are mounted between the struts 110 and 111 adjacent opposite ends of the carriage on horizontal shafts 126. These shafts 126 are secured in place by a round head 127 on one end of each shaft, which heads are counter-sunk into one of the upper bars 111, and by a cotter pin 128 at the opposite end of each shaft. The carriage is also provided with lower, double-flanged wheels 130 mounted adjacent opposite ends of the carriage between the struts;112 and 113 on shafts 131 secured in place by counter-sunk heads 132 and cotter pins 133. The upper wheels 126 ride upon the upper edge of the associated track 101 with their flanges straddling the track, and the lower wheels 130 similarly ride upon the lower edge of the track 101.

The track ltll is pierced at equally spaced apart intervals with four rectangular holes 135, and the carriage is provided with a pivoted locking arm 136 having a stop 141 adapted successively to project into the holes 135 in thetrack 101 to lock the carriage in aligned positions above the four tanks 5, 6, 7, and 8. The pivoted locking arm 136 is mounted on the carriage for movement about a horizontal axis by means of a support 137 fastened to one of the bars 110 by bolts 138 and having a boss 139 at its lower end, and by means of a screw 140 which projects through the locking arm 136 and threadedly engages the boss 139. Upper and lower plates 142 and 143 are respectively secured to the upper bars 110 and 111 and to "the lower bars 112 and 113 by cap screws 144 and project laterally beyond the carriage to provide a mounting for the upper supporting tube of the associated filtering column 35. The upper supporting tube 80 is provided with a rib 146 of rectangular cross section which runs longitudinally of the upper supporting tube 80 and is secured thereto in any suitable manner, as by counter-sunk screws {not shown). Aspht collar 147 (Fig. l) surrounds the upper supporting tube'80 and is provided with flanges 148 on opposite sides of the rib 146, which may be urged to gether by a bolt 149. The collar 147 is thereby securely clamped in position around the upper supporting tube 80 at a point thereon immediately above and adjacent the upper-mounting plate 142 when the filtering column 35 is in its extreme lower position. The mounting plates 142 and 143 have holes therethrough which accommodate for free-sliding vertical movement the supporting tube 80 and its rib 146. When the filtering column 35 is in its extreme lower position, the split collar 147 rests on the upper mounting plate 142and functions as a stop to prevent further downward movement of the column.

A latch 150 is pivotally mounted on the rib 146 of the upper supporting tube 80 adjacent the lower end of the 'rib by means of a screw 151 which passes loosely through the latch 150 and is threaded into the rib 146. The latch 150 consists of a handle portion 152 and two projecting stops 153 and 154, most clearly shown in Fig. 7. The rib 146 is provided with 2. lug 156 secured by means of screws 157'to the rib 146 at a point slightly above the screw 151 on which the latch 150 is mounted.

The pivoted locking arm 136 is substantially L-shaped and comprises a generally horizontal leg 160 and a generally vertical leg 161 having a projection 162 at its lower end. A rod 163 extends laterally from the horizontal leg 160, and one end of a coil spring 165 is attached thereto. The other end of the spring 165 is secured to the lower mounting plate 143. This spring urges the pivoted locking arm 136 in a counterclockwise direction as viewed in Figs. 6 and 7, whereby the stop 141 will be moved into one of the holes 135 in the track 101 when the carriage is aligned above one of the tanks 5, 6, 7 or 8.

When the carriage 100 is in the position shown in solid lines in Fig. l, the projection 141 of the pivoted locking arm 136 on the carriage 100 extends into the first hole inthe track 101, thereby locking the carriage against movement in a horizontal direction to prevent movement of the'filter element 37 into contact with the end wall or partition wall of the slurry tank 5. When it is desired to move the filter element 37 from the slurry tank 5 into the wash tank 6, the operator grasps the filtering columne '35 and raises it vertically until the lug 156 on the rib 146 of the supporting tube 80 engages the lower edge of the horizontal leg 160 of the pivoted, locking arm 136 and moves it in a clockwise direction, as viewed in Figs. 6 and7, to the position shown in Fig. 7. During upward travel of the supporting tube 80, the stop 153 of the latch contacts the lower edge of the projection 162 on the pivoted locking arm 136 and acts as a cam to swing the latch 150 ina clockwise direction, as viewed in Fig. 6, to the position showfithercin in dotted lines, thereby permittingv the latch 150 to pass by the projection 162 and come to rest'in the position shown in Fig. 7. If the filtering column 35 is then permittedby the operator to drop downwardly, the coil spring causes the pivoted locking arm 136 to rotate counterclockwise into the position shown in Fig. 6'with its stop 141 again extending through the first hole 135 in the track 101, and with the latch 150 swung back into the position shown in solid lines in Fig. 6, whereby further downward movement and horizontal movement of the filtering column 35 will both be prevented. T 0 move the filtering column 35 horizontally from its position above the slurry tank 5 to its position above the wash tank 6, the operator again lifts the filtering column 35 until the lug 156 on the rib 146 engages the leg of the pivoted locking arm 136 to rotate it clockwise as viewed in Figs. 6 and 7 and withdraw the stop 141 wash tank 6. Of course, on raising the filtering column out of the slurry tank 5 to its extreme upper position, and while manually supporting the column with the lug 156 bearing against the lower edge of the leg .160 of the locking arm 136 to hold the stop 141 out of the adjacent hole 135, the operator'rnay at once move the column and its supporting carriage horizontally from its position above tank 5 to its position above tank 6. As soon as the stop 141has been moved out of line with the first hole 135, the column 35 should no longer be manually supported. During horizontal travel of the carriage, the stop 141 bears against the side of the track 101 and holds the the third suction tube 83 is mounted, thereby cutting off theflow of air through the filter cake. The filtering column 35 is then lowered until the filter cakeion the filter element 37 contacts the aligned scraper blades'31; "'By additional rotation of the valve housing 53, the filter element 37 is caused to rotate, and the filter cake is scraped therefrom by the scraper blades-31 and falls through the outlet 9 therebelow. The 'arrangement of the holes 72 in the valve disk 68 of thevalveunit 60 along an arch which, in this instance, subtendsan angle of only about 90, leaves more than a suflicientarc through which the valve housing 53 and the filter element 37 may be rotated to scrape a filter cake from the filter element without connecting the valve port 57 with any of the other port (holes 72) of the valve unit. I The filtering column 35 is then again raised 'to hacktreme "upper position andheld with the lug'156 contact ingthe leg 160 of the pivoted locking arm 136,10 hold the latter in the position shown in Fig. 7, whilethe filtering column is moved horizontally 'ba'ck to its initial position as shown in Fig. 1 for repetition of the cycle described. I e a When operated in accordance with the foregoing description, the two filtering columns 34 and 35 merely constitute a plurality of units identical in constructionand function. B'oth columns are o'peratedj'together in the same manner for doubling the filtering capacity obtainable with a single filtering column. Obviously, the number of independent filtering columns could be multiplied as desired for operation in association witha single enlarged receptable, or in association-with a plurality of such receptacles, each designed to accommodate one or more filtering units. v

While I have shown the four tanks 5, 6,-7, and;8 as units of a single large receptacle 1, in order to eliminate cracks or spaces between the tanks inwhich liquid or solid material dropping from the thimble filters could become lodged, it is also obvious that the operation of the filtering units is in no manner dependent "upon this particular arrangement of tanks and thatthe four tanks 5, 6, 7, and 8 could be-constructed and arranged infa variety ofways. In the following claims, the term tanks is intended to be employed in a generic sense"to include a plurality of'indepcndent containers-as well as a plurality of compartments ina single receptacle. i r.

By suitable modification of the tank, valve, and suction tube arrangements, the filtering units described- 'above maybeemployed in any of a variety of ways as may be required by the particular material-to be filtered. In Fig.

10, there is schematically illustrated a modified arrange ment adapted for use when it is desired to re-slurry the precipitate in the wash tank6 for more complete sep aration of residual filtrate retained by the filte'r cake' at the conclusion of the filtration step in the slurry tank 5a In this embodiment of the invention, the filtering 'column 34 of-the embodiment previously described is employed with only slight structural change. One of the suction tubes 82 in the first embodiment, instead of being-employed as a suction tube, serves as apositive pressure tube 82:: for feeding either'air, inert gas, or liquid wash solution to the tliimble filter 36, suppliedfrom any convenient source (not shown); and the third suction tube 83 and the corresponding hole 72 in the valve disk 68, in which the third suction tube 83 was mounted, are -eliminated. The filtering column 35a differs structurally from 12 the filtering column 35 of the embodiment previously described only in that this third suction tube 83, the associated rubber hose 99, and the hole 72 of the disk 68, in which'this suction tube 83 was mounted, are eliminated. i In the embodiment of the invention represented by Fig. 10, the filtering column 34a is employed only in the slurry-and wash tanks 5a and 6, and the filtering column 35tfis' employed only in the wash, drying liquid, and scraper tanks 6, 7a, and 8a. Consequently, the slurry and drying liquid tanks 5a and 7a may be made smaller than the corresponding tanks 5 and 7 in the previous embodiment in order to reduce the volume of liquid required to carry out the filtration step and the drying step, and the scraper tank 8a, containing only a single set of scraper blades, may be similarly reduced in size, as shown. The tank 6 is identical with the corresponding tank 6 in the embodiment previously described. The tracks on which the two filtering columns and their supporting carriages are mounted may, if desired, be shortened to restrict the horizontal movement of the filtering columns to the paths which they must travel in order to cooperate with the tanks with which they are respectively to be associated. The stirringmechanism of the previous embodiment may most conveniently be modified in the present embodiment by merely eliminating the stirrer blade 16 formerly employed in the wash tank 7, and the associated shaft and gear mechanism as Well. The filter element 36 mounted for insertion into the slurry and Wash tanks 5a and 6 is not adapted in this embodiment of the invention to carry a filter cake beyond the wash tank 6, and the associated shield 84, therefore, may be omitted from the filtering column 34a supporting this filter element, and the shield supporting elements may be suitably modified and simplified as desired for cooperating only with the shield on the adjacent filtering column 35a.

In operating the apparatus in accordance with the embodiment of the invention schematically represented by Fig. '10, the two filtering columns 34a and 35a no longer merely constitute a plurality of units identical in construction and function, but cooperate in a single filtering, washing, drying, and scraping cycle. With one of the filtering columns 34a in raised position above the slurry tank 5a and with the other filtering column 35a in raised position above the wash tank 6, the appropriate tanks 5a, 6, and 7a are charged with a slurry to be filtered, a wash solution, and a drying liquid, respectively. The filter element 36 on the filtering column 34a above slurry tank 5a isfirst lowered into thattank. The associated valve unit 60 is .then'manipulated, as hereinbefore described, to place the suction tube 81 in communication with the interior 'of'the filter element 36 to cause a filter cake to be loaded upon the filter element. This condition is represented in Fig. 10 by the arrow in the slurry tank 5a.

After a filter cake of the desired thickness has been collected, the valve unit 60 is manipulated to disconnect the suction tube 81, and the filtering column 34a is raised, moved horizontally to a position above the wash tank 6, and lowered into that tank. The associated valve unit 60 is thenmanipulated to place the positive pressure tube 82a in communication with the interior of the filter element 36a, whereby the selected type of fluid to'be supplied by the positive pressure tube passes through the associated tubes 50 and 45 into the filter element 36 and through the walls of the filter element and into suspension'in the wash solution. This condition is represented in- Fig; 10 by the arrow in the .wash tank 6 pointing into the filtering column 34a. The stirring mechanism in the wash'tank 6 provides sufficient agitation to keep the discharged precipitate in suspension in the wash solution until it can be picked up again on the filter element 37 of the other filtering column 35zz in'a manner to be described. After the filter element 36 has deposited its load into the wash tank 6, the valve unit 60 is manipulated to block off the positive pressure tuhe'82a from communication'with. the associated filter element 36 to cut '03. the.

flow of fluid .therethrough, and the first filtering .column 34a is raised and returned horizontally .tolitsTini'tia'l.,.positionabove the wash tankSa ready'for thernex't cycle.

'The second filtering column 35a ,is then lowered into the wash tank6 and the associated valveunit'fifliismafiipulated to place one of the suction tubes81 in this filtering column in communication with the interior of-the associated filter element 37, whereby suctionisapp'lied' to the interior of this -filter elementto draw wash solution therethrough and to build up afilter cake on'the outside of the filter element. This conditionis represented'in Fig. 10 t by the arrow in the wash tank 6 pointing 'awayfromthe 'filtering column35a. "When a.cake of"thedesired"tliick- *ness' has accumulated, the valve housing 53on.the second filtering column 35a is :rotated to a position such 't'lratthe passageway 7 inthe associated"flow directing disk75 is "blocked by a solid:por.tion'ofthe adjacent valve disk 68, thereby cutting 'off'the :applicationof suction. The sec- 'ond filtering column 35L: is then raised until the stop 9153 on the associated latch 150 arrives in positionto'bearupon the :upper edge of the projectionf-162 'onthecooperat ing =pivoted locking arm 136 and to prevent downward movement of the filtering column. After this filtering column has remained in its raised position-above the wash tank 6 long enough for any dripping :of wash solution from *the filter element'37 to-cease,-'the filtering column is manipulated to move it'horizontally to aposition above-the drying liquid tank '7aand is then lowered'to insert the filter element 37 into this tank. The associatcd'valve'unit 60 ismanipulated to place asecond suction tube-82 in oommunication with the interior of the filter element 37 tosudk drying liquid through the filter cake and through thefilter element and to-exhaust the same through the'connected suctiontube'fiz and ultimately intoa collection tank (not shown). This condition is represented in Fig. I1 O by the iarrowin the drying liquidtan'k7a. Drying liquid is perimitted to be drawn through the filter :cake for a sufiicient time to wash it.substantially-completely freeiromaresidual wash solution.

Whilethe'lastmentioned suctiontubei82 isfstillin com- .muriication with theinteriornf the'filter element 37 ;-and drying liquid is being drawn through-the 'filter :cake the'reon, the filtering :column 35a is again "raised to its extreme upper position :and .moved thorizontally tolthe might "to sa position above the scraper mechanismrin the :scraperitank 8a. The valveunit 60 is manipulated in :the-usual manner to cut off the tube 82 from communication with the interior of the filter element 37 after sufficient air :'has been sucked through the filter cake to remove substantially all of the drying liquid therefrom and to leave the filter cake in a dry condition.

The filtering column 35a is thenlowereduntil thefilter cake on the filter element .37 contacts theiscraper blades 31 in the scraper :tank Set. By additionalirotation'ofthe valve housing 53, the filter element 37 iscaused to rotate and the filter cake is scraped therefrom by :the scraper blades 31 and falls through'the outlet 9therebelow. After removal of the filter cake from the .filter element .37, the filtering column 35a is raised to its extreme upper position and moved horizontally back .to its initial ;position .above the wash tank 6 for operationas described above in the succeedingcycle.

When operating in accordance with this embodiment ofthe invention, it is apparent that asubstantial amount of precipitate mustbe held up in the wash-tank6 by *reason of theinability .of the filter element 37-.on :the second filtering column 35a completely to remove it. Eachttime the filter element 36 on the first filtering column 34a discharges the filter cake picked up by it in the slurry tank 5a, suflicient additional precipitate is added to that remaining from the previous cycle to permit the filter-element 37 .on the second filtering column 350 .to pickup a cake of normal size. The disadvantage of having a hold- .up of precipitate in the wash tank 6 and two filtering columns instead of one to carry out asing'le .cycle of filtering columns .281, 82, and 83 and operation must be-weighed :against the. advantageu esultingfrom the greater washing eificiency obtainediby reslurrying the precipitate from onefilterelement to another filter element in the Wash solution in order to determine whether or not the present embodiment of the invention is to be preferred'for .a particular type of service. Llt should also be noted that the amount of wash solution initially chargedin'to the wash tank6 should befsuch that the addition of wash solutionthroug'ha filter e'lemenbto discharge into the Wash tank 6'the cake picked upfront the slurry in the s'lurryitan'k Sa -(when 'wa'sh solution rather than 'a gas is usedforithis purpose) does not cause "the ln' Fig. 11, there is schematically illustrated another modified "arrangement adapted for use when it is "desired to reslurrytheprecipitate injeither or both of the Wash solution and'dryingfliquid'tanks. For this embodimento'f the invention,"the-'onlystructural changes required in *the apparatus employed in the embodiment "represented by Fig.19 involve incorp orating two additional tubes within'the r pper tubular support of 'each filtering column 34b -and 35b. In accordance with'tliis embodiment of the invention, the two filtering columns again nrerely "con- 's'titute *aplurality of'units identical in constructionand tion of one'of the filterin'g columns 34bw'ill be described,

itbeingtunder'stood that the construction and' operation of the otherfiltering column 351;, and er any additional which may desirably "be added to the sarrangementgmerelyduplicate the construction and opera- 1=tion otfilterin'g column "3941).

.Referring to filter ing column-34b, three su ction'tlibes V two positive pr'essu're tubes and 18312 for :supplying Jfluid under pressure -'-are contained in the upper fsupporiting tube '80 in th'e relative positions shown till Fig. '11; scribed, zis modifiedamerely by' the provision "of two *addi The valve disk 68, previously de- Etional :holes .72, ap'osition'edto accommoda'teft'h'e two addi- .tional alZUbIES, land the lower en ds o'f thefive tubes are respectively soldered or otherwise rigidly securedin the' fiverholes 72. The three suction tubes 81, 82, and '83, communicating with suitable sources of suction as before, are adapted to 'draw filtrate, wash liquid, respectively, through :thezthimb'le filter 36 and to discharge them respectively into solution, and drying collection tanks (not shown). The tube-82b :serveslas a supply-'lineffor feed- .ing under pressure lair, inert gas, or Wash solution, 'to the filter-element 36, and the tube 83b serves'as a 's'upply line .for .feeding under pressure 1 air, inert gas, *or dryin'g liquid to the filter element.

While the filtering column 34b is in rits lloc'ked posi- .tion .above the .slurry tank -5, theappropriate tanks 5, ,6, and 7 are respectively charged as before with slurry, wash solution, and drying liquid. In lthisinst'an'ce, a .smaller amount of wash solution may ibe put into the ,wash tank-'6, and *a smaller amount of drying liquid may be put into the drying liquid tank 7 than in the first embodiment described herein, depending ?upon whether liquid ortgasisto be supplied to these tanks from the positivelpressure tubes 82b and :831 respectively, during the cycle to be-described. V v

The filtering column 34b is first lowered into the ,slurry .tank -5, and the valve u'nit '60 is manipulated to :place.-one of the suction tubes '81 into communication with the interior of the filter'elemen't 36, whereby a filter .cake is loaded upon thefilter elementas filtrate is drawn therethrough :and is ultimately discharged into'a receiving tank (not shown). This condition is represented in 'Fig. 11 by the arrows inthe slurry tank 5. When a filter .cake .of the desired thickness ha-s accummulated on "the filter element 36, the valve unit 60 is manipulated to cut,

terior of the filter element to discharge the filter cake therefrom and cause the precipitate to be reslurried in the wash tank 6. This condition is represented in Fig. 11 by the arrows in the wash tank 6 pointing into the filtering columns. With the filter element 36 still in the wash tank 6, the valve unit 60 is again manipulated to place a second suction tube 82 into communication with the interior of the filter element 36, whereby wash solution is drawn through the filter element and ultimately discharged into a receiving tank (not shown) and a second 'filter cake is loaded upon the filter element. This condition is represented in Fig. 11 by the arrows in the wash tank 6 pointing away from the filtering columns.

The filtering column 34b is then returned to its locked raised position above the wash tank 6.

After dripping from the filter element 36 into the wash tank 6 has ceased, the filtering column 34b is moved horizontally to its position above the drying liquid tank 7 and is lowered to insert the filter element 36 into this tank, at which time the valve unit 60 is manipulated to place the second positive pressure tube 83b in communication with the interior of the filter element 36 to force the selected fluid under pressure through the filter element and to discharge the filter cake and reslurry it in the drying liquid tank 7. This condition is represented in Fig. 11 by the arrows in the drying liquid tank 7 pointing into the filtering columns. The valve unit 60 is then manipulated to place the third suction tube 83 in communication with the interior of the filter element 36, whereby drying liquid is drawn through the filter element and ultimately discharged into a receiving tank (not shown), and a filter cake is again caused to be loaded upon the filter element. This condition is represented in Fig. 11 by the arrows in the drying liquid tank 7 pointing away from the filtering colums. With the third suction tube 83 still in communication with the interior of the filter element 36, the filtering column 341) is raised and moved horizontally to its next locked position above the scraper tank 8, whereby air is drawn through the filter cake to carry off all of the drying liquid retained thereby to leave the filter cake in a dry condition.

The filtering column 34b is then lowered until the filter cake on the filter element 36 contacts the scraper blades 31 in this tank. By additional rotation of the valve housing 53, the filter element 36 is caused to rotate, and the filter cake is scraped therefromby the scraper blades 31 and falls through the outlet 9 therebelow. I

While the arrangement of the five holes 72 in the valve disk 68 of the valve unit 60 to accommodate the five tubes housed within the upper tubular support 80 requires that they be spaced around the valve disk 68 over a substantially larger arc than in the first embodiment disclosed herein, there is still sufiicient space to allow more than the approximately 90 of rotationof the valve housing 53 required to remove a filter cake from the filter element without. placing any of the suction or positive pressure tubes in communication with the interior of the filter element. a j

.It is obvious that one of thepositive pressure tubes 826 or 83b, and its associated hole 72 in the valve disk 68, may be eliminated from each filter column in order to the apparatus is adapted alone to perform simultaneously eliminate one of the reslurrying operations, in which case M paratus represented by Fig. 10.

As is the case when employing the reslurrying operation described in connection with the embodiment represented'by Fig. 10, the reslurrying operations just described 7 necessitate a hold-up of precipitate in the wash and drying liquid tanks 6 and 7 because of the inability of the filter elements to remove all of the precipitate suspended in the liquids contained in these tanks. In each instance the additional precipitate added to that left in a tank during a preceding cycle of operation is sufiicient to enable the filter elements again to pick up from that tank a filter cake of normal thickness. As before, the hold-up of precipitate is a disadvantage to be weighed against the advantages'of res'lurrying to obtain more eflicient washing of the precipitate. With the embodiment represented by Fig. 11, however, it is possible to employ a reslurrying type of operation in which only a single filtering column is required to complete a full cycle. Thus the embodiment represented by Fig. 11 is more economical "as to [apparatus required than that represented by Fig.

In order to illustrate how suction and pressure may be applied to the appropriate pressure difierential conduits which are adapted to be placed in communication with the interior of the hollow filter elements for opera tion according to each of the three embodiments of the present invention, there is shown in Fig. 12 a flow dithe necessary portions of the arrangement shown in Fig.

In the embodiment of the invention represented by Fig. 11, each of the filtering columns 34b and 35b includes fivepressu're difierential conduits, three of which 81, 82, and 83,'are sequentially employed in conjunction with suitable sources of suction for drawing liquid through the associated filter element into separate collection tanks, and two of which, 82b and 8312, are respectively employed in conjunction with fluid reservoirs arid a positive pressure pump to force a suitable fluid (gas or liquid) into the'interior of the associated filter element and outwardly through the walls thereof into the wash tank 6 and the drying liquid tank 7. In Fig.

' 12, the two filtering columns 34b and 35b are shown diagrammatically, with the respectively associated filter elements 36 and 37 communicating with separate valve units and with the five pressure difierential conduits 81,

82b, 82, 83b, and 83 of each filtering column leading away from the associated valve unit. The suction conduits 81, 82, and 83 respectively lead into collection tanks 201,202, and 203, and extend downwardly therein to points near the bottoms thereof.' These collection tanks should be airtight so that a partial vacuum may be maintained therein above the level of the liquid collected therein. Three suction conduits 211, 212, and 213, communicating respectively with the collection tanks 201, 202, and 203. through the tops thereof, lead to a suction manifold 214; which is in turn connected with a vacuum pump 204. With this arrangement the vacuum "pump 204 serves to maintain a partial vacuum in the tanks 201, 202, and 203 so that when one of the valve units 60ismanipulated .to place a selected suction conduit 8 1, 82, or 83 incommunication with the interior of an associated filter element 36 or 37 in one of the three 'liquid containing tanks 5, 6, and 7, liquidsurrounding ithe filter element is drawn therethrough and into the tank 201, 202, or 203 to which the selected suction conduit is arrears connected. Siinilarly -the -positive pressutegcouduits 82b and 83]) 'lead respectively to pressure .tanks andzllti. Dependinguponwhether air, inert gas, .ora. suitable hq' uid is. to be -force'dthrough. the filter elements when; they are in the wash tank 6 and the drying; liquidtank 7 ;to unload filter cakes therefromythe. pressureetanks .205

and20j6 may contain either air,.-inert;gas;: or.-liquid., Ase

of operation of the apparatus, but sufiiciently lirnited to t I leave an air space above the liquid level in each pressure tanlu: Positive pressure 'conduitsxZIS-i; and 216, cOmmunicatingqespectively ,with. theetwopressure tanks 20 and 206 'tliiough the tops thereof, lead t p fi ssure manifold -217 which-is m turn connected toapdsitive pressure pump-107 adapted -topump; air or, inertp gas through the pressure manifold -2I7 'and the pressureconduits -21 5 and 216 'tomaintain -a-positive pressure above the liquid level-in-each of'the pressure tanks1205fand 206. When aseIectedpositive pressure conduitgfizb or 83b is placed-in communication with; the interior, of anassociated filter element bymanipulation .of. 'tl1e.associate'd valve unit 60, liquid isforced,fronntheassociated-tank 205- or 206, as the case may be,'; throug'h the selected positive pressure conduit and ultimatelyiinto the interior of the associated filter element 36 or 37 and outwardly thrOugh the walls thereof. Conventional valves 220 may be placed at various points in. the ectionand" pressure lines described above in order that any part of the system may be isolated at will.

For the purpose of demonstrating the particular utility of the apparatus disclosed herein, reference is made to the copending application of Robert Q. Boyer, Serial No. 577,380, filed February 12, 1945. In that application, there is disclosed a complete plant process for treating a calutron wash solution containing uranium enriched with the U isotope to recover, with negligible losses to the outside, all of the uranium contained in the solution. By the term calutron is meant an apparatus having as its basic components a vacuum chamber, electrodes for accelerating ions, an ion source, a magnetic field to bend the trajectory of the ions, and a collector for capturing and retaining the ions. The wash solution of the calutron is the solution resulting from washing the surfaces thereof for the purpose of removing materials deposited therein during operation thereof. In the'process described in that application, there is produced a slurry of uranous oxalate consisting of as the precipitate suspended in a 1 N to 3 N hydrochloric acid solution containing ions of Fe++, Cr+++, Ni++,

Cu++, and perhaps a trace of U++++, and un-ionized H2C2O4. It is necessary that the precipitate of woman-51120 be separated from positive metal ions by filtration and washing, and, since the uranium in the precipitate is enriched with U which it is the entire object ofthe process to recover without loss, the exercise of extreme care for a 1 is isipereolatedifl mugh. the. filter. cake forv the a purpose .of

displacing residual oxalic. acid .washsolutionand carrying :water of; hydration to convert the V recovery -0f, U.(.C2Q4-),2IH2Q from thejsus e'n'. ,o U CzQ la-fiHaO mane hydroa chlorieaci'cl solution. er'r'ing' for example, to the. em: bodiment of theinven 11 described in Figs. 1- to19 hereof; heslurrytebe" filtered is charged into the. slurry f' the. oxa'il'ic'jacid .was'hsolutionis .charged into the wash tanle'fi, iand'thelniethyl alcohol is. charged into the. drying'l'liquiditank 7. The apparatus. is thenumanip ljla eXaCtlY as, described above .in. disclosing therstruce in: an .o'perationeoff this embodiment of the invention. i'nstancesfin which there is specified-abovels, mm which parts of the apparatus should becjonis ructed, thelselection ofv materials was. made with the Boyeep qcess in mind.., Whenehandling diiierent slurri ",,,wash solutions, and drying llqllldspphangfid-till the 's' ecified' materials. may be: desirable ,to Prevent; at: fatal; of ertainparts of the apparatus; -bythe-.liquids in Contact .tlierewitha I The embodiments of .the :present inventionydesc rihed withreferenceto-Eigs. .IO- and; 11 are -.equally- :welladapted h. -dlingi thedltCaOaQz-fiHzO slurry in quest-ionraud s ess. e. added;advantage thatreslurrying iu thetwash tear, 'or'i'n both the wash and drying liquid tanks,;,ef: fects a more thorough elimination of the metal impurities present in the original slurry without increasing the cost of the apparatus out of proportion to the advantage obtained for relatively large scale operations.

In the light of the foregoing disclosure, it will be apparent that various modifications of be made. It is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention and I do not therefore desire to limit the invention to the exact details shown except in so far as they may be defined in the following claims.

What is claimed is:

l. Filtering apparatus comprisinga hollow porous filter element having an opening atone end, a non-porous closure secured to said filter element and closing the open end thereof, a valve unit having a rotatable porlion carrying a first port and a non-rotatable portion 55 carrying a plurality of additional ports, a first tubular structure secured at one end to said closure and supporting said filter element. and secured at its opposite end to the rotatable portion of saidrvalve unit, a first conduit housed within said first tubular structure and projecting atone end through said closure into communication with the interior of said-filter element and communicating at its opposite end with said first port, a see -ond tubular structure secured at one end to the nonrotatable portion of said valve unit for supporting said.

firsttubular structure and said valve unit, and a plurality of pressure diiferential conduits corresponding to the number of said additional ports extending into said second tubular structure and into communication respectively with said additional ports, said valve unit being operable by rotation of the rotatable portion thereof to place said first port in communication with said addi-- tional ports individually in a predetermined sequence.

2. Filtering apparatus comprising a tubular filter support, a hollow porous filter element having an opening at one end, a filter head comprising a tubular member .-.1admirably adaptedtol perthe invention may 19 closed at one end by a generally disk-shaped end wall having a central aperture therein and closed at its opposite end by a generally disk-shaped endwall having an apertured boss centrally located therein, said filt'er element being mounted on said first end wall with its end opening closed thereby, a first conduit mounted in communication with the aperture in the boss on said second end wall and extending through said tubular member and through the aperture in said first end, wall into communication with the interior of said filter element, said filter head being secured for ready detachment to one endof said tubular filter support, and a.,s'econd conduit 1 housed within said tubular filter support, "the'j boss'of said second end wall of said filter head being arranged to engage one end of said second conduit in said supporting column and to constitute a'coupling" between it and said first conduit in said'filter'head 3. Filtering apparatus comprising a hollow porous filter element having an openingfat one end, a non-porous closure secured to said filter element and closing the open end thereof, a' first tubular structure" secured at one'end to said closure and supporting said' filter' element, avalve unit secured to the other end of said first tubular struc ture, a first conduit housed within said first tubular structure and projecting at one end through said closure into the interior of said filter element and communicating at itsopposite end with said valve unit,"a second tubular structure secured at one end to said valve unit and supporting said valve unit and said first tubular structure, a plurality of pressure differential conduits extending into said second tubular structure and communicating with said valve unit, a first port in said valve unit communicating continuously with said first conduit, and a 'r'ot'atable passageway in said valve unit-continuously communicating with said first port and adapted to communicate with each of said conduits individually in a predetermined sequence.

4. A pressure differential filtering apparatus comprisinga 'verticallyhiovable tubular support mounted upon a supporting framework, a hollow porous filterelement rotatably mounted on'said tubular support, avalve unit having a rotatable portion attached to said filter element and a non-rotatable portion attached to said tubular support, a tube communicating with'one side of said valve unit and extending into the interior of said filter element, a plurality of conduits'housed within said tubular support and communicating with the other side'of said valve unit, and a passage through the rotatable portion of said valve'unit adapted to place said tube in communication with-each ofsaid plurality of conduits individually in a predetermined sequence upon rotation 'of the filter element-.1 4 V v 5 References Cited in the file of this patent UNITED STATES PATENTS 167,880 Donning Sept. 21, 1875 450,204 Warden, Apr. 14, 1891 524,155 Williamson et al Aug. 7, 1894 743,652 Moore Nov. 10, 1903 887,268 Porter et al May 12, 1908 919,628 I Oliver Apr. 27, 1909 945,193 Ridgway: Ian. 4, 1910 1,051,620 Neil Ian. 28, 1913 1,198,216 'Hansjon Sept. 12, 1916 1,378,929 Wurs'cher I May 24, 1921 1,429,913 Keene Sept. 19, 1922 1,548,160 Newman Aug. 4, 1925 2,068,257 Banks et a1. Jan. 19, 1937 2,371,895 Kingman MarJZO, 1945 2,381,462 Naugle .Q Aug. 7, 1945 

